1. Field of the Invention
The present invention relates to an indicating apparatus and more particularly it relates to an indicating apparatus of the type in which measured values correlated with some physical quantity are stepwise indicated by optical means.
2. Description of the Prior Art
What forms the background of the present invention is, for example, an apparatus for indicating measured values provided by a weighing machine. Conventionally, for the purpose of indicating measured values, suitable converter means is used to convert a measured value into a visual physical quantity, so that the measured value is indicated in terms of such physical quantity. In the case of a weighing machine, such visual quantity is, for example, the amount of movement of a pointer or the amount of movement of a graduated plate. Therefore, the measured value is recognized by reading the graduation pointed by a pointer. In case where measured values are indicated in an analog manner by cooperation between the graduated plate and the pointer, as described above, it is rarely that a graduation and the pointer come into alignment with each other, thus making it necessary to judge to which graduation the pointer lies nearest, i.e. to make an arithmetical processing of the figures in specified less significant digits, such as rounding, i.e. the operation of dropping decimal figures to the right of a specified number of digits after increasing the final remaining figure by 1 if the first digit dropped is 5 or greater, which is a troublesome operation.
If a continuous physical quantity as described above is represented in a digital manner, it is possible for an operator to read out the measured value at a glance. For this reason, there have been proposed various indicating apparatuses for electronically processing physical quantities correlated with measured values and representing them in a digital manner. Such digital indicating apparatus, however, has to use a large number of expensive electronic circuits and hence apparatuses, such as weighing machines, incorporating it therein are expensive.
Examples of the prior art which has solved the above problem by optical means and which is of particular interest to the present invention will now be described.
As a technique of particular interest to the present invention, mention may be made of Japanese Patent Publication No. 15033/69 entitled "Indicating Apparatus for Indicating Weight and the Like", published on July 4, 1969. It does not provide a purely digital representation, however, and it is an improvement of an optical projecting apparatus including lenses for magnifying graduations and an array of numerals corresponding thereto movable in accordance with measured values and projecting the relevant graduation the numerals corresponding thereto, comprising a light shielding plate disposed in the optical path of the optical projecting apparatus for shielding the light in a predetermined range, so that the image is projected on a suitable screen. Thus, the graduated plate is provided with numerals laterally of the graduations such that the numerals correspond to the latter and the graduation and numerals will be projected on the screen. Since the graduations except the one corresponding to the numerical value which has been rounded (in the sense described above) are shielded, only one graduation is projected on the screen. Therefore, by reading the numeral corresponding to this graduation, the rounded measured value is obtained. The control of the movement of the shield plate is achieved, for example, by a solenoid in connection with an arithmetically rounding mechanism.
Another technique of interest to the present invention is U.S. Pat. No. 3,461,986, which discloses an apparatus for providing a digital indication of postal rates variable stepwise in accordance with the weight of postal matter, said apparatus being affixed to a postal weighing machine. The apparatus for providing a digital indication of postal rates is related to the present invention, and it works on the principle of the two-way switching of a reflecting mirror associated with a series of postal rate-indicating numerals movable depending upon the weight of postal matter, so as to optically provide a digital indication of the postal rate in a readout window.
In the prior techniques described above, however, the means for selecting the graduation or numeral to be indicated, i.e., the means for selecting the numeral corresponding to the rounded measured value is realized by the movement of the shield plate or the two-way switching of the reflecting mirror driven by a solenoid or the like. This implies the presence of movable parts, which in turn complicate the mechanical construction, causing problems including breakdown and wear. Further, the prior art apparatuses are disadvantageous in that power is needed to drive the solenoid and particularly when an electric battery is used to drive the same, the battery is consumed very much.